1. Field of the Invention
The present invention generally relates to an ignition coil device for an engine of, for example, an automobile and more specifically to an ignition coil assembly that includes a plurality of ignition coils, which are connected to corresponding spark plugs securely installed in plug holes of the engine.
2. Description of Related Art
For example, Japanese Unexamined Patent Publication No. 9-250437 discloses an integrated connector block, in which connectors for supplying electricity to corresponding ignition coils are integrated. The integrated connector block includes a connector block main body, which is formed as an elongated body made of a resin material. Coil connectors are integrally formed in a lower surface of the connector block main body. Each ignition coil, which is secured to a corresponding spark plug installed in an engine, is installed to and is thus engaged with a corresponding one of the coil connectors in an axial direction of the corresponding ignition coil, i.e., in an axial direction of the corresponding spark plug.
Furthermore, in order to allow installation of the ignition coils to the plug holes of the engine in a single step, an ignition coil assembly, which includes a plurality of ignition coils arranged at predetermined intervals, has been proposed. For example, as shown in FIG. 8, one such ignition coil assembly 51 includes a resin base member 53 that holds a plurality of ignition coils 52 at corresponding positions, which correspond to positions of plug holes 131 of an engine 130. Each ignition coil 52 may be threadably secured to the base member 53 through use of a bolt. Alternatively, each ignition coil 52 and the base member 53 may be integrally molded using a resin material. In either way, each ignition coil 52 and the base member 53 are integrated together. Thereafter, the ignition coil assembly 51 is installed to the engine 130 by axially installing the ignition coils 52 into the corresponding plug holes 131, and longitudinal ends and the center of the base member 53 are secured to the engine 130 by bolts 53c. The bolts 53c are received through corresponding through holes 53a of the base member 53 and are threadably engaged with screw holes 132 of the engine 130.
However, in the previously proposed ignition coil assembly 51, manufacturing errors in the intervals (plug hole pitches) of the plug holes 131 of the engine 130 and manufacturing errors in the intervals (securing point pitches) of the ignition coils 52 need to be minimized, resulting in a difficulty in manufacturing of the ignition coil assembly. That is, when there is a substantial deviation between the plug hole pitches of the plug holes 131 and the securing point pitches of the ignition coils 52, it could happen that each ignition coil 52 secured to the base member 53 cannot be linearly inserted into the corresponding plug hole 131.
The present invention addresses the above disadvantage. Thus, it is an objective of the present invention to provide an ignition coil assembly that allows sliding adjustment of a securing position of each ignition coil in an imaginary plane that is perpendicular to an axis of the ignition coil.
To achieve the objective of the present invention, there is provided an ignition coil assembly for an engine. The engine includes a plurality of plug holes, each of which receives a corresponding one of a plurality of spark plugs. The ignition coil assembly includes a plurality of ignition coils, a base cover, a top cover and a temporarily fastening member. The ignition coils are arranged to be electrically connected to the spark plugs, respectively. Each ignition coil includes a head and a main body, which extends from the head. The base cover includes a plurality of receiving through holes, which penetrate through the base cover and are arranged at corresponding positions that correspond to positions of the plug holes, respectively. The main body of each ignition coil is received through a corresponding one of the receiving through holes such that a gap is defined between the main body of each ignition coil and an inner peripheral wall of the corresponding one of the receiving through holes. The head of each ignition coil is supported by the base cover around a peripheral edge of the corresponding one of the receiving through holes. The top cover covers a top surface of the base cover and secures each ignition coil through engagement with the head of each ignition coil. The temporarily fastening member temporarily fastens the top cover and the base cover in a manner that allows sliding adjustment of a securing position of each ignition coil in an imaginary plane that is perpendicular to an axis of each ignition coil.